WordNet records no synonym and no antonym for liberalism. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a political orientation that favors social progress by reform and by changing laws rather than by revolution
an economic theory advocating free competition and a self-regulating market
Synonyms, antonyms and the broader and narrower relations for liberalism come from Princeton University’s WordNet. Full sources and licences.